Effect of acute exposure of Hg and Zn on survival of native and invasive Artemia from wild populations exposed to different degrees of environmental contamination

In recent decades, brine shrimps of the genus Artemia has suffered a major biodiversity loss in the Mediterranean region due to the introduction of the highly invasive A. franciscana. Pollution has been proposed as an important factor limiting this global invasion. Contrary to the general acceptation that pollution tends to favour invasive species, it has been postulated that local adaptation of native Artemia to pollution may prevent or delay colonization by the exotic species. To provide insight into this “pollution resistance hypothesis”, we investigated the individual effect of acute toxicity of mercury (Hg) and zinc (Zn) on the survival of six different native and invasive Artemia populations from the Iberian Peninsula collected from areas with different levels of Hg- and Zn-pollution. The Hg and Zn 24 h-LC50 values for Artemia nauplii of the different populations varied between 20 and 70 mg Hg L, and between 350 and 450 mg Zn L, respectively. Native Artemia from Cabo de Gata (SW Spain) showed significantly higher survival at high Hg concentrations than other populations, which may be explained by the longer history of Hg-pollution in that area from mining activities, compared to the other sites. In contrast, differences between populations in response to high Zn levels were weak, and inconsistent with the environmental differences in Zn concentrations. Discussion of the results of this work was done in relation to the “pollution resistance hypothesis” and conclude that Hg pollution may limit the invasion by A. franciscana in some study sites for an uncertain length of time